stk-code/lib/wiiuse/dynamics.c

/*
 *	wiiuse
 *
 *	Written By:
 *		Michael Laforest	< para >
 *		Email: < thepara (--AT--) g m a i l [--DOT--] com >
 *
 *	Copyright 2006-2007
 *
 *	This file is part of wiiuse.
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 3 of the License, or
 *	(at your option) any later version.
 *
 *	This program is distributed in the hope that it will be useful,
 *	but WITHOUT ANY WARRANTY; without even the implied warranty of
 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *	GNU General Public License for more details.
 *
 *	You should have received a copy of the GNU General Public License
 *	along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *	$Header$
 *
 */

/**
 *	@file
 *	@brief Handles the dynamics of the wiimote.
 *
 *	The file includes functions that handle the dynamics
 *	of the wiimote.  Such dynamics include orientation and
 *	motion sensing.
 */

#include "dynamics.h"

#include <math.h>                       /* for atan2f, atanf, sqrt */
#include <stdlib.h>                     /* for abs */


/**
 *	@brief Calculate the roll, pitch, yaw.
 *
 *	@param ac			An accelerometer (accel_t) structure.
 *	@param accel		[in] Pointer to a vec3b_t structure that holds the raw acceleration data.
 *	@param orient		[out] Pointer to a orient_t structure that will hold the orientation data.
 *	@param rorient		[out] Pointer to a orient_t structure that will hold the non-smoothed orientation data.
 *	@param smooth		If smoothing should be performed on the angles calculated. 1 to enable, 0 to disable.
 *
 *	Given the raw acceleration data from the accelerometer struct, calculate
 *	the orientation of the device and set it in the \a orient parameter.
 */
void calculate_orientation(struct accel_t* ac, struct vec3b_t* accel, struct orient_t* orient, int smooth) {
	float xg, yg, zg;
	float x, y, z;

	/*
	 *	roll	- use atan(z / x)		[ ranges from -180 to 180 ]
	 *	pitch	- use atan(z / y)		[ ranges from -180 to 180 ]
	 *	yaw		- impossible to tell without IR
	 */

	/* yaw - set to 0, IR will take care of it if it's enabled */
	orient->yaw = 0.0f;

	/* find out how much it has to move to be 1g */
	xg = (float)ac->cal_g.x;
	yg = (float)ac->cal_g.y;
	zg = (float)ac->cal_g.z;

	/* find out how much it actually moved and normalize to +/- 1g */
	x = ((float)accel->x - (float)ac->cal_zero.x) / xg;
	y = ((float)accel->y - (float)ac->cal_zero.y) / yg;
	z = ((float)accel->z - (float)ac->cal_zero.z) / zg;

	/* make sure x,y,z are between -1 and 1 for the tan functions */
	if (x < -1.0f) {
		x = -1.0f;
	} else if (x > 1.0f) {
		x = 1.0f;
	}
	if (y < -1.0f) {
		y = -1.0f;
	} else if (y > 1.0f) {
		y = 1.0f;
	}
	if (z < -1.0f) {
		z = -1.0f;
	} else if (z > 1.0f) {
		z = 1.0f;
	}

	/* if it is over 1g then it is probably accelerating and not reliable */
	if (abs(accel->x - ac->cal_zero.x) <= ac->cal_g.x) {
		/* roll */
		x = RAD_TO_DEGREE(atan2f(x, z));

		orient->roll = x;
		orient->a_roll = x;
	}

	if (abs(accel->y - ac->cal_zero.y) <= ac->cal_g.y) {
		/* pitch */
		y = RAD_TO_DEGREE(atan2f(y, z));

		orient->pitch = y;
		orient->a_pitch = y;
	}

	/* smooth the angles if enabled */
	if (smooth) {
		apply_smoothing(ac, orient, SMOOTH_ROLL);
		apply_smoothing(ac, orient, SMOOTH_PITCH);
	}
}


/**
 *	@brief Calculate the gravity forces on each axis.
 *
 *	@param ac			An accelerometer (accel_t) structure.
 *	@param accel		[in] Pointer to a vec3b_t structure that holds the raw acceleration data.
 *	@param gforce		[out] Pointer to a gforce_t structure that will hold the gravity force data.
 */
void calculate_gforce(struct accel_t* ac, struct vec3b_t* accel, struct gforce_t* gforce) {
	float xg, yg, zg;

	/* find out how much it has to move to be 1g */
	xg = (float)ac->cal_g.x;
	yg = (float)ac->cal_g.y;
	zg = (float)ac->cal_g.z;

	/* find out how much it actually moved and normalize to +/- 1g */
	gforce->x = ((float)accel->x - (float)ac->cal_zero.x) / xg;
	gforce->y = ((float)accel->y - (float)ac->cal_zero.y) / yg;
	gforce->z = ((float)accel->z - (float)ac->cal_zero.z) / zg;
}

static float applyCalibration(float inval, float minval, float maxval, float centerval) {
	float ret;
	/* We don't use the exact ranges but the ranges + 1 in case we get bad calibration data - avoid div0 */
	if (inval == centerval) {
		ret = 0;
	} else if (inval < centerval) {
		ret = (inval - centerval) / (centerval - minval + 1);
	} else {
		ret = (inval - centerval) / (maxval - centerval + 1);
	}
	return ret;
}

/**
 *	@brief Calculate the angle and magnitude of a joystick.
 *
 *	@param js	[out] Pointer to a joystick_t structure.
 *	@param x	The raw x-axis value.
 *	@param y	The raw y-axis value.
 */
void calc_joystick_state(struct joystick_t* js, float x, float y) {
	float rx, ry, ang;

	/*
	 *	Since the joystick center may not be exactly:
	 *		(min + max) / 2
	 *	Then the range from the min to the center and the center to the max
	 *	may be different.
	 *	Because of this, depending on if the current x or y value is greater
	 *	or less than the associated axis center value, it needs to be interpolated
	 *	between the center and the minimum or maxmimum rather than between
	 *	the minimum and maximum.
	 *
	 *	So we have something like this:
	 *		(x min) [-1] ---------*------ [0] (x center) [0] -------- [1] (x max)
	 *	Where the * is the current x value.
	 *	The range is therefore -1 to 1, 0 being the exact center rather than
	 *	the middle of min and max.
	 */
	rx = applyCalibration(x, js->min.x, js->max.x, js->center.x);
	ry = applyCalibration(y, js->min.y, js->max.y, js->center.y);
	/* calculate the joystick angle and magnitude */
	ang = RAD_TO_DEGREE(atan2f(ry, rx));
	js->ang = ang + 180.0f;
	js->mag = sqrtf((rx * rx) + (ry * ry));
}


void apply_smoothing(struct accel_t* ac, struct orient_t* orient, int type) {
	switch (type) {
		case SMOOTH_ROLL: {
				/* it's possible last iteration was nan or inf, so set it to 0 if that happened */
				if (isnan(ac->st_roll) || isinf(ac->st_roll)) {
					ac->st_roll = 0.0f;
				}

				/*
				 *	If the sign changes (which will happen if going from -180 to 180)
				 *	or from (-1 to 1) then don't smooth, just use the new angle.
				 */
				if (((ac->st_roll < 0) && (orient->roll > 0)) || ((ac->st_roll > 0) && (orient->roll < 0))) {
					ac->st_roll = orient->roll;
				} else {
					orient->roll = ac->st_roll + (ac->st_alpha * (orient->a_roll - ac->st_roll));
					ac->st_roll = orient->roll;
				}

				return;
			}

		case SMOOTH_PITCH: {
				if (isnan(ac->st_pitch) || isinf(ac->st_pitch)) {
					ac->st_pitch = 0.0f;
				}

				if (((ac->st_pitch < 0) && (orient->pitch > 0)) || ((ac->st_pitch > 0) && (orient->pitch < 0))) {
					ac->st_pitch = orient->pitch;
				} else {
					orient->pitch = ac->st_pitch + (ac->st_alpha * (orient->a_pitch - ac->st_pitch));
					ac->st_pitch = orient->pitch;
				}

				return;
			}
	}
}